Excavating – Ditcher – Condition responsive
Reexamination Certificate
2001-10-29
2003-05-20
Pezzuto, Robert E. (Department: 3671)
Excavating
Ditcher
Condition responsive
C180S019300
Reexamination Certificate
active
06564481
ABSTRACT:
FILED OF THE INVENTION
This invention relates to an electric vehicle having left and right electric motors driving left and right driven wheels.
BACKGROUND OF THE INVENTION
“Utility machine” is a term which refers generally to dollies used for loading and unloading; cultivators and tractors used in farming; mowers for cutting grass; and snow-removers and soon. Among utility machines there are electric vehicles propelled by electric motors. An electric vehicle of this kind is referred to in Japanese Patent Laid-Open Publication No.SHO-50-107619, “Steering Control Apparatus of Electric Dolly”. This electric dolly is shown in
FIG. 27
hereof.
In
FIG. 27
, left and right electric motors (not shown) of an electric dolly
200
drive left and right driven wheels
201
L,
201
R to propel the electric dolly
200
along a path
202
. When while the electric dolly
200
is traveling it deviates from the path
202
and a left side sensor
204
L touches a left side slope
203
L, the right side electric motor reverse-rotates to change the direction of the electric dolly
200
so that it returns to the path
202
.
When the electric dolly
200
deviates from the path
202
and a right side sensor
204
R touches a right side slope
203
R, the left side electric motor reverse-rotates to change the direction of the electric dolly
200
so that it returns to the path
202
.
However, because the electric dolly
200
starts to change direction only after one of the left and right sensors
204
L,
204
R has made contact with the respective slope
203
L or
203
R, it deviates relatively far from the path
202
before changing direction. Consequently, the electric dolly
200
snakes as it travels.
This snaking can be prevented by the driver changing the direction of the electric dolly
200
before either of the left and right sensors
204
L,
204
R touches the respective slope
203
L or
203
R. However, for the driver to change the direction of the electric dolly
200
without relying on the left and right sensors
204
L and
204
R, it is necessary for the driver to grip an operating handle
205
strongly and turn the electric dolly
200
with great force.
Changing the direction of the electric dolly
200
without relying on the left and right sensors
204
L and
204
R like this puts a large burden on the driver.
Also, when the driver changes the direction of the electric dolly
200
by force, the electric dolly
200
becomes unsteady and difficult to keep in a good traveling attitude.
To overcome this, electric vehicles having left and right electric motors driving left and right driven wheels and left and right brakes for adjusting the speeds of the left and right driven wheels have been proposed, as for example in Japanese Patent Publication No. SHO-48-4260, “Direction and Propulsion Control Apparatus of Electric Car”. With this electric car, transit control is possible whereby when an operating lever is pushed forward the car accelerates; when the operating lever is pulled backward the car is braked or reverses; when the operating lever is pushed to the left the right rear wheel accelerates but the left rear wheel is braked or reverses; and when the operating lever is pushed to the right the left rear wheel accelerates but the right rear wheel is braked or reverses. This transit control is carried out by the operating lever being operated to directly alter the settings of multiple potentiometers and thereby control respective electric currents supplied to the left and right electric motors.
However, in this case, the supplies of power to the left and right electric motors are altered in correspondence with the angle of inclination of the operating lever, essentially irrespective of the speed of the vehicle. And consequently, for example with an electric dolly, although there is no problem when the speed of the dolly is low, if the operating lever is operated when the speed is high, the dolly is liable to turn excessively due to inertial force.
Another electric vehicle having left and right electric motors driving left and right driven wheels appears in for example Japanese Patent Publication No. SHO-57-43003, “Motor Control Apparatus of Electric Car”. In an electric vehicle having a driving motor for each of a pair of wheels, this control apparatus inputs speed detection signals from speed detectors provided on each motor to a differential amplifier, and on the basis of this differential output controls the speed of one of the motors in correspondence with speed fluctuations of the other motor.
When the electric vehicle hits an irregularity in the road surface or a slope, the speed of one of the wheels may drop. When this happens without correction, the electric vehicle turns to the right or the left instead of moving straight forward, which is undesirable. To avoid this, with the control apparatus mentioned above, the speeds of the left and right wheels are matched, and consequently the electric vehicle does not turn on its own as a result of the state of the road surface.
In the above-mentioned Japanese Patent Publication No. SHO-57-43003, it is explained that when the operating shaft is tilted to the left or the right a speed difference between the left and right electric motors is generated and the electric vehicle turns to the left or the right. But in this case, it is difficult to distinguish whether the cause of a speed difference arising between the left and right wheels is an external one originating in the condition of the road surface or a human-initiated one (the operating shaft being operated). To make this distinction an electronic distinguishing circuit is needed, and electronic distinguishing circuits of this kind are complicated and costly, and even then the reliability of their distinguishing is not said to be high.
An invention relating to a rotary snow-clearing vehicle is disclosed in Japanese Patent Laid-Open Publication No. SHO-51-137214, “Control Method of Rotary Snow-Clearing Vehicle having Automatic Speed Control Apparatus”. In this control method, which is suitable for a rotary snow-clearing vehicle which travels on rails, the load on an engine for clearing snow is detected with a sensor, and the transit speed of the rotary snow-clearing vehicle is controlled on the basis of this detection signal. In the case of a rotary snow-clearing vehicle which simply moves forward or backward along rails, there is no problem; but with a snow-clearing machine for clearing snow from an ordinary road, because the vehicle body rocks to the left and the right under the action of the road surface and snow, the driver must constantly control the vehicle to the forward direction. Consequently, with a snow-clearing machine for ordinary roads, the control method mentioned above cannot be employed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electric vehicle with which it is possible to make direction adjustments and turns of the electric vehicle without putting a burden on the driver and it is possible to make direction adjustments and turns with the electric vehicle in a stable state.
To achieve this object and other objects, a first aspect of the invention provides an electric vehicle having: a vehicle body; a left electric motor, mounted on the vehicle body, for driving a left driven wheel; a left brake, mounted on the vehicle body, for braking the left driven wheel; a right electric motor, mounted on the vehicle body, for driving a right driven wheel; a right brake, mounted on the vehicle body, for braking the right driven wheel; left and right control handles extending rearward from the vehicle body; left and right grips provided at the ends of the control handles; a left speed control lever, provided alongside the left grip, for controlling the left electric motor and the left brake; and a right speed control lever, provided alongside the right grip, for controlling the right electric motor and the right brake.
Left and right speed control levers are provided alongside left and right grips, and a left brake and electric motor are controlle
Bungo Keiichiro
Hanafusa Jitsumi
Inui Tsutomu
Kanke Hiroo
Kuroiwa Kenji
Adams & Wilks
Honda Giken Kogyo Kabushiki Kaisha
Pezzuto Robert E.
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